527 lines
16 KiB
C++
527 lines
16 KiB
C++
/*
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Copyright (c) 2010-2013, Arvid Norberg
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All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions
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are met:
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* Redistributions of source code must retain the above copyright
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notice, this list of conditions and the following disclaimer.
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* Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in
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the documentation and/or other materials provided with the distribution.
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* Neither the name of the author nor the names of its
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contributors may be used to endorse or promote products derived
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from this software without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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POSSIBILITY OF SUCH DAMAGE.
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*/
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#ifndef TORRENT_BLOCK_CACHE
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#define TORRENT_BLOCK_CACHE
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#include <boost/unordered_set.hpp>
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#include <boost/cstdint.hpp>
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#include <boost/shared_ptr.hpp>
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#include <boost/shared_array.hpp>
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#include <list>
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#include <vector>
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#include "libtorrent/time.hpp"
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#include "libtorrent/error_code.hpp"
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#include "libtorrent/io_service_fwd.hpp"
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#include "libtorrent/hasher.hpp"
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#include "libtorrent/sliding_average.hpp"
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#include "libtorrent/time.hpp"
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#include "libtorrent/tailqueue.hpp"
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#include "libtorrent/linked_list.hpp"
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#include "libtorrent/disk_buffer_pool.hpp"
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#include "libtorrent/file.hpp" // for iovec_t
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#if TORRENT_USE_ASSERTS
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#include "libtorrent/disk_io_job.hpp"
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#endif
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namespace libtorrent
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{
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struct disk_io_job;
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class piece_manager;
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struct disk_buffer_pool;
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struct cache_status;
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struct block_cache_reference;
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struct counters;
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namespace aux { struct session_settings; }
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struct alert_dispatcher;
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#if TORRENT_USE_ASSERTS
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class file_storage;
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#endif
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#if TORRENT_USE_ASSERTS
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struct piece_log_t
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{
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piece_log_t(int j, int b= -1): job(j), block(b) {}
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int job;
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int block;
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// these are "jobs" thar cause piece_refcount
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// to be incremented
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enum artificial_jobs
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{
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flushing = disk_io_job::num_job_ids, // 20
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flush_expired,
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try_flush_write_blocks,
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try_flush_write_blocks2,
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flush_range,
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clear_outstanding_jobs,
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set_outstanding_jobs,
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last_job
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};
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static char const* job_names[7];
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};
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char const* job_name(int j);
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void print_piece_log(std::vector<piece_log_t> const& piece_log);
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#endif
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struct TORRENT_EXTRA_EXPORT partial_hash
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{
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partial_hash(): offset(0) {}
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// the number of bytes in the piece that has been hashed
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int offset;
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// the sha-1 context
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hasher h;
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};
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struct cached_block_entry
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{
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cached_block_entry()
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: buf(0)
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, refcount(0)
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, dirty(false)
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, pending(false)
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{
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#if TORRENT_USE_ASSERTS
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hashing_count = 0;
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reading_count = 0;
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flushing_count = 0;
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#endif
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}
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char* buf;
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enum { max_refcount = (1 << 30) - 1 };
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// the number of references to this buffer. These references
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// might be in outstanding asyncronous requests or in peer
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// connection send buffers. We can't free the buffer until
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// all references are gone and refcount reaches 0. The buf
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// pointer in this struct doesn't count as a reference and
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// is always the last to be cleared
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boost::uint32_t refcount:30;
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// if this is true, this block needs to be written to
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// disk before it's freed. Typically all blocks in a piece
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// would either be dirty (write coalesce cache) or not dirty
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// (read-ahead cache). Once blocks are written to disk, the
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// dirty flag is cleared and effectively turns the block
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// into a read cache block
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boost::uint32_t dirty:1;
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// pending means that this buffer has not yet been filled in
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// with valid data. There's an outstanding read job for this.
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// If the dirty flag is set, it means there's an outstanding
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// write job to write this block.
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boost::uint32_t pending:1;
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#if TORRENT_USE_ASSERTS
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// this many of the references are held by hashing operations
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int hashing_count;
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// this block is being used in this many peer's send buffers currently
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int reading_count;
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// the number of references held by flushing operations
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int flushing_count;
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#endif
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};
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// list_node is here to be able to link this cache entry
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// into one of the LRU lists
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struct TORRENT_EXTRA_EXPORT cached_piece_entry : list_node
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{
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cached_piece_entry();
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~cached_piece_entry();
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bool ok_to_evict(bool ignore_hash = false) const
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{
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return refcount == 0
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&& piece_refcount == 0
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&& num_blocks == 0
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&& !hashing
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&& read_jobs.size() == 0
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&& outstanding_read == 0
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&& (ignore_hash || !hash || hash->offset == 0);
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}
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// storage this piece belongs to
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boost::shared_ptr<piece_manager> storage;
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// write jobs hanging off of this piece
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tailqueue jobs;
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// read jobs waiting for the read job currently outstanding
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// on this piece to complete. These are executed at that point.
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tailqueue read_jobs;
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int get_piece() const { return piece; }
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void* get_storage() const { return storage.get(); }
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bool operator==(cached_piece_entry const& rhs) const
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{ return storage.get() == rhs.storage.get() && piece == rhs.piece; }
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// if this is set, we'll be calculating the hash
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// for this piece. This member stores the interim
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// state while we're calulcating the hash.
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partial_hash* hash;
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// set to a unique identifier of a peer that last
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// requested from this piece.
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void* last_requester;
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// the pointers to the block data. If this is a ghost
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// cache entry, there won't be any data here
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boost::shared_array<cached_block_entry> blocks;
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// the last time a block was written to this piece
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// plus the minimum amount of time the block is guaranteed
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// to stay in the cache
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//TODO: make this 32 bits and to count seconds since the block cache was created
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time_point expire;
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boost::uint64_t piece:22;
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// the number of dirty blocks in this piece
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boost::uint64_t num_dirty:14;
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// the number of blocks in the cache for this piece
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boost::uint64_t num_blocks:14;
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// the total number of blocks in this piece (and the number
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// of elements in the blocks array)
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boost::uint64_t blocks_in_piece:14;
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// ---- 64 bit boundary ----
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// while we have an outstanding async hash operation
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// working on this piece, 'hashing' is set to 1
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// When the operation returns, this is set to 0.
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boost::uint32_t hashing:1;
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// if we've completed at least one hash job on this
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// piece, and returned it. This is set to one
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boost::uint32_t hashing_done:1;
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// if this is true, whenever refcount hits 0,
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// this piece should be deleted
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boost::uint32_t marked_for_deletion:1;
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// this is set to true once we flush blocks past
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// the hash cursor. Once this happens, there's
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// no point in keeping cache blocks around for
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// it in avoid_readback mode
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boost::uint32_t need_readback:1;
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// indicates which LRU list this piece is chained into
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enum cache_state_t
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{
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// this is the LRU list for pieces with dirty blocks
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write_lru,
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// this is the LRU list for volatile pieces. i.e.
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// pieces with very low cache priority. These are
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// always the first ones to be evicted.
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volatile_read_lru,
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// this is the LRU list for read blocks that have
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// been requested once
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read_lru1,
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// the is the LRU list for read blocks that have
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// been requested once recently, but then was evicted.
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// if these are requested again, they will be moved
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// to list 2, the frequently requested pieces
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read_lru1_ghost,
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// this is the LRU of frequently used pieces. Any
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// piece that has been requested by a second peer
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// while pulled in to list 1 by a different peer
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// is moved into this list
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read_lru2,
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// this is the LRU of frequently used pieces but
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// that has been recently evicted. If a piece in
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// this list is requested, it's moved back into list 2.
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read_lru2_ghost,
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num_lrus
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};
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boost::uint32_t cache_state:3;
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// this is the number of threads that are currently holding
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// a reference to this piece. A piece may not be removed from
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// the cache while this is > 0
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boost::uint32_t piece_refcount:7;
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// if this is set to one, it means there is an outstanding
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// flush_hashed job for this piece, and there's no need to
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// issue another one.
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boost::uint32_t outstanding_flush:1;
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// as long as there is a read operation outstanding on this
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// piece, this is set to 1. Otherwise 0.
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// the purpose is to make sure not two threads are reading
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// the same blocks at the same time. If a new read job is
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// added when this is 1, that new job should be hung on the
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// read job queue (read_jobs).
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boost::uint32_t outstanding_read:1;
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// the number of blocks that have >= 1 refcount
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boost::uint32_t pinned:16;
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// ---- 32 bit boundary ---
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// the sum of all refcounts in all blocks
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boost::uint32_t refcount;
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#if TORRENT_USE_ASSERTS
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// the number of times this piece has finished hashing
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int hash_passes;
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// this is a debug facility to keep a log
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// of which operations have been run on this piece
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std::vector<piece_log_t> piece_log;
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bool in_storage;
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bool in_use;
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#endif
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};
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// internal
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inline std::size_t hash_value(cached_piece_entry const& p)
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{
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return std::size_t(p.storage.get()) + std::size_t(p.piece);
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}
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struct TORRENT_EXTRA_EXPORT block_cache : disk_buffer_pool
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{
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block_cache(int block_size, io_service& ios
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, boost::function<void()> const& trigger_trim
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, alert_dispatcher* alert_disp);
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private:
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typedef boost::unordered_set<cached_piece_entry> cache_t;
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public:
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typedef cache_t::iterator iterator;
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typedef cache_t::const_iterator const_iterator;
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// returns the number of blocks this job would cause to be read in
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int pad_job(disk_io_job const* j, int blocks_in_piece
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, int read_ahead) const;
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void reclaim_block(block_cache_reference const& ref);
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// returns a range of all pieces. This migh be a very
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// long list, use carefully
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std::pair<iterator, iterator> all_pieces() const;
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int num_pieces() const { return m_pieces.size(); }
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list_iterator write_lru_pieces() const
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{ return m_lru[cached_piece_entry::write_lru].iterate(); }
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int num_write_lru_pieces() const { return m_lru[cached_piece_entry::write_lru].size(); }
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// mark this piece for deletion. If there are no outstanding
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// requests to this piece, it's removed immediately, and the
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// passed in iterator will be invalidated
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void mark_for_deletion(cached_piece_entry* p);
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// similar to mark_for_deletion, except for actually marking the
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// piece for deletion. If the piece was actually deleted,
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// the function returns true
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bool evict_piece(cached_piece_entry* p, tailqueue& jobs);
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// if this piece is in L1 or L2 proper, move it to
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// its respective ghost list
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void move_to_ghost(cached_piece_entry* p);
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// returns the number of bytes read on success (cache hit)
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// -1 on cache miss
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int try_read(disk_io_job* j, bool expect_no_fail = false);
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// called when we're reading and we found the piece we're
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// reading from in the hash table (not necessarily that we
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// hit the block we needed)
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void cache_hit(cached_piece_entry* p, void* requester, bool volatile_read);
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// free block from piece entry
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void free_block(cached_piece_entry* pe, int block);
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// erase a piece (typically from the ghost list). Reclaim all
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// its blocks and unlink it and free it.
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void erase_piece(cached_piece_entry* p);
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// bump the piece 'p' to the back of the LRU list it's
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// in (back == MRU)
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// this is only used for the write cache
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void bump_lru(cached_piece_entry* p);
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// move p into the correct lru queue
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void update_cache_state(cached_piece_entry* p);
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// if the piece is marked for deletion and has a refcount
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// of 0, this function will post any sync jobs and
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// delete the piece from the cache
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bool maybe_free_piece(cached_piece_entry* p);
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// either returns the piece in the cache, or allocates
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// a new empty piece and returns it.
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// cache_state is one of cache_state_t enum
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cached_piece_entry* allocate_piece(disk_io_job const* j, int cache_state);
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// looks for this piece in the cache. If it's there, returns a pointer
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// to it, otherwise 0.
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cached_piece_entry* find_piece(block_cache_reference const& ref);
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cached_piece_entry* find_piece(disk_io_job const* j);
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cached_piece_entry* find_piece(piece_manager* st, int piece);
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// clear free all buffers marked as dirty with
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// refcount of 0.
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void abort_dirty(cached_piece_entry* p);
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// used to convert dirty blocks into non-dirty ones
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// i.e. from being part of the write cache to being part
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// of the read cache. it's used when flushing blocks to disk
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void blocks_flushed(cached_piece_entry* pe, int const* flushed, int num_flushed);
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// adds a block to the cache, marks it as dirty and
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// associates the job with it. When the block is
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// flushed, the callback is posted
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cached_piece_entry* add_dirty_block(disk_io_job* j);
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enum { blocks_inc_refcount = 1 };
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void insert_blocks(cached_piece_entry* pe, int block, file::iovec_t *iov
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, int iov_len, disk_io_job* j, int flags = 0);
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#if TORRENT_USE_INVARIANT_CHECKS
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void check_invariant() const;
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#endif
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// try to remove num number of read cache blocks from the cache
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// pick the least recently used ones first
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// return the number of blocks that was requested to be evicted
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// that couldn't be
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int try_evict_blocks(int num, cached_piece_entry* ignore = 0);
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// if there are any dirty blocks
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void clear(tailqueue& jobs);
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void update_stats_counters(counters& c) const;
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#ifndef TORRENT_NO_DEPRECATE
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void get_stats(cache_status* ret) const;
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#endif
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void set_settings(aux::session_settings const& sett);
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enum reason_t { ref_hashing = 0, ref_reading = 1, ref_flushing = 2 };
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bool inc_block_refcount(cached_piece_entry* pe, int block, int reason);
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void dec_block_refcount(cached_piece_entry* pe, int block, int reason);
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int pinned_blocks() const { return m_pinned_blocks; }
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#if TORRENT_USE_ASSERTS
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void mark_deleted(file_storage const& fs);
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#endif
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private:
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// returns number of bytes read on success, -1 on cache miss
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// (just because the piece is in the cache, doesn't mean all
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// the blocks are there)
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int copy_from_piece(cached_piece_entry* p, disk_io_job* j, bool expect_no_fail = false);
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void free_piece(cached_piece_entry* p);
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int drain_piece_bufs(cached_piece_entry& p, std::vector<char*>& buf);
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// block container
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cache_t m_pieces;
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// linked list of all elements in m_pieces, in usage order
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// the most recently used are in the tail. iterating from head
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// to tail gives the least recently used entries first
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// the read-list is for read blocks and the write-list is for
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// dirty blocks that needs flushing before being evicted
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// [0] = write-LRU
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// [1] = read-LRU1
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// [2] = read-LRU1-ghost
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// [3] = read-LRU2
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// [4] = read-LRU2-ghost
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linked_list m_lru[cached_piece_entry::num_lrus];
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// this is used to determine whether to evict blocks from
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// L1 or L2.
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enum cache_op_t
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{
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cache_miss,
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ghost_hit_lru1,
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ghost_hit_lru2
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};
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int m_last_cache_op;
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// the number of pieces to keep in the ARC ghost lists
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// this is determined by being a fraction of the cache size
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int m_ghost_size;
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// the number of blocks in the cache
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// that are in the read cache
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boost::uint32_t m_read_cache_size;
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// the number of blocks in the cache
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// that are in the write cache
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boost::uint32_t m_write_cache_size;
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// the number of blocks that are currently sitting
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// in peer's send buffers. If two peers are sending
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// the same block, it counts as 2, even though there're
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// no buffer duplication
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boost::uint32_t m_send_buffer_blocks;
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// the number of blocks with a refcount > 0, i.e.
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// they may not be evicted
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int m_pinned_blocks;
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#if TORRENT_USE_ASSERTS
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std::vector<std::pair<std::string, void const*> > m_deleted_storages;
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#endif
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};
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}
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#endif // TORRENT_BLOCK_CACHE
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